Systems and methods for selecting serving gateways to service user equipment

ABSTRACT

Some embodiments provide methods for selecting a serving gateway to service user equipment in communication with a network, including: receiving a message from a base transceiver station including a list of tracking areas handled by the base transceiver station, initiating a domain name system query for at least one tracking area in the list of tracking areas to identify information indicating a serving gateway serving the at least one tracking area, storing, in local memory, the information indicating the serving gateway serving the at least one tracking area, and upon an occurrence of a triggering event, retrieving, from the local memory, the stored information indicating the serving gateway serving the at least one tracking area.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation patent application of, and claims thebenefit of the earlier filing date of, U.S. patent application Ser. No.12/603,698, entitled “Systems and Methods for Selecting Serving Gatewaysto Service User Equipment,” filed on Oct. 22, 2009, which is herebyexpressly incorporated by reference in its entirety.

This application is related to U.S. patent application Ser. No.12/603,704, titled “Systems and Methods for Classifying User Equipmentand Selecting Tracking Areas,” to Kamalaraj; U.S. patent applicationSer. No. 12/603,710, titled “Systems and Methods for Reduced LatencyTracking Area Selection,” to Dakshayani, filed on Oct. 22, 2009; U.S.patent application Ser. No. 12/603,802, titled “Systems and Methods forSelecting Tracking Areas and Reducing Paging,” to Kamalaraj, filed onOct. 22, 2009; and U.S. patent application Ser. No. 12/603,712, titled“Systems and Methods for Selecting Tracking Areas and Reducing TrackingArea Updates,” to Kamalaraj, filed on Oct. 22, 2009, each of which ishereby expressly incorporated by reference herein in its entirety.

TECHNICAL FIELD

The disclosed subject matter relates to systems and methods forselecting serving gateways and tracking areas to serve user equipment.

BACKGROUND

Wireless networks are telecommunications networks that use radio wavesto carry information from one node in the network to one or morereceiving nodes in the network. Wired communication can also be used inportions of a wireless network, such as between cells or access points.Cellular telephony is characterized by the use of radio cells thatprovide radio coverage for a geographic area, with multiple cellsarranged to provide contiguous radio coverage over a larger area.

The first generation of wireless telephone technology used analog mobilephones in which analog information signals were transmitted. Astechnology progressed a second generation (2G) of wireless service wasintroduced. In 2G systems, digital information signals were used tomodulate a carrier. These 2G technologies used time division multiplexedaccess (TDMA) or code division multiple access (CDMA) technologies todistinguish multiple users. Such networks that were upgraded to handlehigher-speed packet data in networks referred to as 2.5G and 3Gnetworks. The 3rd Generation Partnership Project (3GPP) and the 3rdGeneration Partnership Project 2 (3GPP2) respectively developed theGSM/UMTS/HSDPA and cdmaOne/CDMA2000 technologies. The next evolution is4G technology, which is referred to as long term evolution-systemarchitecture evolution (LTE-SAE) and uses orthogonal frequency divisionmultiple access (OFDMA) technology.

Other wireless protocols have also developed including WiFi, animplementation of various IEEE 802.11 protocols, WiMAX, animplementation of IEEE 802.16, and HiperMAN, which is based on an ETSIalternative to IEEE 802.16.

Wireless communication technologies are used in connection with manyapplications, including, for example, satellite communications systems,portable digital assistants (PDAs), laptop computers, and user equipment(e.g., cellular telephones, mobile phones equipment). One benefit thatusers of such applications can obtain is the ability to connect to anetwork (e.g., the Internet) as long as the user is within range of sucha wireless communication technology.

SUMMARY

Some embodiments of the disclosed subject matter provide reduced latencysystems and methods for selecting serving gateways to serve userequipment. Some embodiments of the disclosed subject matter providereduced latency systems and methods for generating user equipment'stracking area identity lists. Some embodiments of the disclosed subjectmatter provide systems and methods for generating user equipment'stracking area identity lists based on, for example, one or more of theuser equipment's paging load, tracking area update load, and mobilitycharacteristics.

Some embodiments provide methods for selecting a serving gateway toservice user equipment in communication with a network, including:receiving a message from a base transceiver station including a list oftracking areas handled by the base transceiver station; performing adomain name system query for at least one tracking area in the list oftracking areas to retrieve and store in a local memory informationidentifying a serving gateway serving the at least one tracking area;receiving an attach request from the base transceiver stationidentifying the user equipment and a tracking area from which the userequipment is connected to the network; searching the informationidentifying a serving gateway serving the at least one tracking areastored in the local memory to identify a serving gateway to service theuser equipment based on the tracking area from which the user equipmentis connected to the network; and sending a message identifying theidentified serving gateway to the base transceiver station.

Some embodiments provide methods for selecting a serving gateway toservice user equipment in communication with a network in which anaccess gateway receives messages from base transceiver stationsincluding a list of tracking areas handled by the base transceiverstation, and wherein the access gateway performs a domain name systemquery for at least one tracking area in the list of tracking areas toretrieve and store in a local memory information identifying a servinggateway serving the at least one tracking area, the method comprising:receiving an attach request from the base transceiver stationidentifying the user equipment and a tracking area from which the userequipment is connected to the network; searching the informationidentifying a serving gateway serving the at least one tracking areastored in the local memory to identify a serving gateway to service theuser equipment based on the tracking area from which the user equipmentis connected to the network; and sending a message identifying theidentified serving gateway to the base transceiver station.

Some embodiments provide a mobility management entity in a communicationnetwork including a local memory; a first interface which is configuredto receive messages from a base transceiver station including a list oftracking areas handled by the base transceiver station, and receive anattach request from the base transceiver station identifying userequipment and a tracking area from which the user equipment is connectedto the network; a second interface which configured to perform a domainname system query for at least one tracking area in the list of trackingareas to retrieve information identifying a serving gateway serving theat least one tracking area; the mobility management entity configured tostore the retrieve information identifying a serving gateway serving theat least one tracking area in the local memory; and search theinformation identifying a serving gateway serving the at least onetracking area stored in the local memory to identify a serving gatewayto service the user equipment based on the tracking area from which theuser equipment is connected to the network; and the first interfacefurther configured to send a message identifying the identified servinggateway to the base transceiver station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a long term evolution (LTE) network in accordancewith some embodiments of the disclosed subject matter.

FIG. 2 illustrates relationships between cells, tracking areas, andevolved nodeBs in accordance with some embodiments of the disclosedsubject matter.

FIG. 3 illustrates a method for selecting a serving gateway to serviceuser equipment in communication with a network in accordance with someembodiments of the disclosed subject matter.

FIG. 4 illustrates a graph of nodes representing tracking areasconnected by weighted edges representing movement of user equipmentbetween the tracking areas in accordance with some embodiments of thedisclosed subject matter.

FIG. 5 is an adjacency matrix describing the graph of FIG. 4

FIG. 6 illustrates a method for allocating a tracking area identity listto user equipment based on the graph of FIG. 4 or matrix of FIG. 5 inaccordance with some embodiments of the disclosed subject matter.

FIGS. 7-9 are adjacency matrixes that are generated as the method ofFIG. 6 is applied to the adjacency matrix of FIG. 5.

FIG. 10 illustrates a table identifying tracking areas, the evolvednodeBs that support those tracking areas, and the tracking area group towhich each tracking area belongs in accordance with some embodiments ofthe disclosed subject matter.

FIG. 11 illustrates a directed adjacency matrix for interconnecting thetracking areas of FIG. 10.

FIG. 12 illustrates a method for allocating a tracking area identitylist to user equipment based on the table of FIG. 10 and matrix of FIG.11 in accordance with some embodiments of the disclosed subject matter.

FIG. 13 illustrates a method of collecting data describing userequipment related behavior, classifying user equipment based on thebehavior, and allocating a tracking area identity list to user equipmentbased on the classification in accordance with some embodiments of thedisclosed subject matter.

DETAILED DESCRIPTION

FIG. 1 illustrates a long term evolution (LTE) network and a universalmobile telecommunication system (UMTS) release 8 network. The networkdiagram of FIG. 1 includes user equipment (UE) 110, an evolved nodeB(eNB) 112, a nodeB 114, a radio network controller (RNC) 116, a mobilitymanagement entity (MME)/user plane entity (UPE) 118, a systemarchitecture evolution gateway (SAE GW) 120, a policy and charging rulesfunction (PCRF) 122, home subscriber server (HSS) 124, core IP network126, internet 128, and Serving General packet radio service Support Node(SGSN) 130. The MME 118, SAE GW 120, and SGSN 130 can be implemented ina chassis as described below. The SAE GW 120 can include a servinggateway (S-GW) as well as a packet data network gateway (P-GW). In someembodiments, the S-GW and P-GW can be implemented on separate networkdevices.

MME 118 is a control-node for the LTE access network. The MME 118 isresponsible for UE 110 tracking and paging procedures includingretransmissions. MME 118 handles the bearer activation/deactivationprocess and is also responsible for choosing the S-GW for a UE 110 atthe initial attach and at time of an intra-LTE handover. The MME 118authenticates the user by interacting with the HSS 124. The MME 118generates and allocates temporary identities to UEs and terminatesNon-Access Stratum (NAS) signaling. The MME 118 checks the authorizationof the UE 110 to camp on the service provider's Public Land MobileNetwork (PLMN) and enforces UE roaming restrictions. The MME 118 is thetermination point in the network for ciphering/integrity protection forNAS signaling and handles the security key management. Lawfulinterception of signaling is also supported by the MME 118. The MME alsoprovides the control plane function for mobility between LTE and 2G/3Gaccess networks with the S3 interface terminating at the MME 118 fromthe SGSN 130. The MME 118 also terminates the S6a interface towards thehome HSS for roaming UEs.

The S-GW routes and forwards user data packets, while also acting as themobility anchor for the user plane during inter-eNB handovers and as theanchor for mobility between LTE and other 3GPP technologies (terminatingS4 interface and relaying the traffic between 2G/3G systems and PDN GW).For idle state UEs, the S-GW terminates the down link data path andtriggers paging when down link data arrives for the UE 110. The S-GWmanages and stores UE contexts, e.g., parameters of the IP bearerservice and network internal routing information. The S-GW also performsreplication of the user traffic in case of lawful interception. The P-GWprovides connectivity to the UE 110 to external packet data networks bybeing the point of exit and entry of traffic for the UE 110. A UE 110may have simultaneous connectivity with more than one P-GW for accessingmultiple packet data networks. The P-GW performs policy enforcement,packet filtering for each user, charging support, lawful interception,and packet screening. The P-GW also provides an anchor for mobilitybetween 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA 1Xand EvDO). The S-GW or the PGW depending on the embodiment, can be usedto provide deep packet inspection and provide advertising to the user ona per subscriber basis as described above on a chassis implementing aS-GW or a PGW.

Tracking Area Lists And Paging

A radio tower is logically located between user equipment 110 and eNB112. One or more such radio towers provide wireless coverage to an areaknown as a cell. Logical grouping of these cells can form trackingareas, for example, that define a boundaries used for paging, roamingrestrictions, etc. Each hexagon of FIG. 2 represents a cell.

Each of the three different fill types of the cells identifies thetracking area in which the cell is located. While each cell is part ofonly one tracking area, an eNB 112 can serve cells belonging todifferent tracking areas. FIG. 2 illustrates nine eNBs 112, each servingthe three cells immediately surrounding a particular eNB 112 (as groupedby the thick black lines). For example, eNB 201 serves cells 211, 212,and 213. The nine eNBs are located within three tracking areas (trackingareas 221, 222, and 223). eNB 201, for example, has cells belonging onlyto tracking area 221. eNB 203, for example, has cells belonging to allthree tracking areas.

When eNB 203, for example, connects to an MME 118, it sends MME 118tracking area identities for each of tracking areas 221, 222, and 223. Atracking area identity (TAI) is used to identify a tracking area, and isconstructed from the MCC (Mobile Country Code), MNC (Mobile NetworkCode), and TAC (Tracking Area Code). A UE 112 can store a list oftracking area identities (“TAI list”) identifying which tracking areasit is served by. The TAI list can be assigned or updated by an MME 118when, for example, the UE 110 connects to a network, on a periodicbasis, or when the UE detects is has entered a tracking area not in itsTAI list and sends a tracking area update (“TAU”).

A UE 110 can receive a page request, for example, to notify the UE thatanother device (e.g., another UE, a landline phone, etc) is trying tocall the UE or to alert the UE that another device is attempting to sendthe UE packet data. For example, data can be received at S-GW 120 from aremote device. S-GW 120 can generate and send a page request to MME 118to locate and establish communications with a UE 110. In response, MME118 can send a page to eNBs 112 in the tracking area where the target UE110 was last known to be located. If the UE 110 receives the pagerequest, the UE can send a paging response to the MME 118 and a processof, e.g., exchanging data or setting up a call, can continue.

An MME 118 can assign a TAI list to a UE based on, among other things,for example, the UE's TAU load and/or paging load. Various embodimentsof the disclosed subject matter provide systems and methods forassigning TAI lists to a UE 112. For low mobility devices, for example,the assigned TAI list can be generated such that the number ofassociated eNBs 112 is reduced. This can reduce unnecessary paging thatcan result from, for example, paging too many eNBs even though a lowmobility device (e.g., an at-home device) may almost always be servicedby the same eNB 112. For high mobility, low paged devices, (e.g.,in-vehicle security devices), for example, the assigned TAI list can begenerated to be associated with a large number of eNBs 112. Because highmobility, low paged devices are rarely paged, few network resources arewasted by paging a large TAI list. Instead, the focus of assigning a TAIlist can be on reducing the number of tracking area updates, which cantend to occur frequently when a high mobility device has a small TAIlist. For high mobility, high paged devices, for example, reaching abalance between reducing paging load and reducing tracking area updatescan be the focus of assigning a TAI list. In addition, eNBs belonging toa same tracking area typically have connectivity to a same S-GW. Variousembodiments of the disclosed subject matter provide systems and methodsfor selecting an S-GW 120 to serve a UE 110.

Reducing Latency For S-GW Selection

An MME 118 is responsible for selecting an S-GW 120 that services thetracking area from which a UE 110 is connecting. For example, when a UE110 sends an Attach Request to an eNB 112, the eNB 112 passes thisrequest to an MME 118, which selects an S-GW 120 to service the UE 110.3GPP standards specify that domain name system (DNS) based mechanisms beused to determine which S-GWs can serve a particular tracking area. Forexample, the list of S-GWs servicing a tracking area can be obtained byperforming a DNS resolution using a TAI fully qualified domain name.Some embodiments reduce latency that can be caused by determining whichS-GWs can serve a particular tracking area.

Referring to FIG. 3, when an eNB 112 connection is established to an MME118, S1 SETUP messages are exchanged for S1 connection initialization.These messages, exchanged between an eNB 112 and an MME 118, areillustrated as messages 301-306 in FIG. 3. S1 Setup Request 306 includesa list of tracking areas handled by eNB 112 (for example, referring toFIG. 2, only TA1 if eNB 201). The MME 118 can use this list of trackingareas to perform DNS queries to obtain and store TAI to S-GW mappings.Later, the stored mappings can be used for S-GW selection, for example,during a UE Attach procedure, Tracking area update procedure, etc. Forexample, Attach Request message 307 from UE 110 to eNB 112 results ineNB 112 sending Attach Request 308 to MME 118. MME 118 can select anS-GW from its locally stored list of S-GWs, handled by this particulareNB 112 and serving the tracking area from which the particular eNB 112is connected. In addition, to address changes in the DNS server, an MME118 can use timers to periodically refresh its locally stored TAI toS-GW mappings.

Table 1 below illustrates and example structure of TAI to S-GW mappings.

TABLE 1 TAI-1 S-GW1 TAI-2 S-GW4 S-GW2 TAI-3 S-GW2 TAI-4 S-GW1 S-GW3The information can be stored in an MME 118 and indicates, for example,that tracking area TAI-2 is served by S-GW4 and S-GW2.

Reducing Latency For TAI List Generation

In assigning a TAI list to a UE 110, the MME can ensure that trackingareas in its assigned TAI list are serviced by the S-GW servicing theUE. Whether a given S-GW services a particular tracking area can bedetermined by performing a DNS resolution using a TAI fully qualifieddomain name. However, doing so for every TAI in a TAI list during listallocation can result in undesired latency. For example, to reducelatency for TAI list allocation in an LTE/SAE network, some embodimentsperform DNS queries as a result of eNB 112 setup.

During processing of an S1 SETUP Request or NAS Attach Request, an MME118 can perform DNS queries to determine which S-GWs service whichtracking areas. The MME 118 can use this information to generate andlocally store the list of TAIs serviced by each S-GW. For example, withreference to Table 2, an MME 118 can store information indicating thatTAI-1, TAI-2, TAI-3, and TAI-4 are served by S-GW1.

TABLE 2 S-GW1: TAI-1 TAI-2 TAI-3 TAI-4 S-GW2: TAI-11 TAI-12 TAI-13TAI-14

When a UE 110 initiates an Attach Request, the list of TAI associatedwith the same S-GW as the tracking area where the UE is located can beused as the set from which to select the tracking area list to be sentto the UE. For example, when a UE 110 initiates an Attach Request, from,for example, TAI-2, the MME 118 can access the information illustratedin Table 2 to determine that TAI-2 is serviced by S-GW1, and that S-GW-1also services TA-1, TAI-3, and TAI-4. The TAI's for the TAI list to beallocated to the UE 112 can be selected from the set of TA-1, TAI-2,TAI-3, and TAI-4, and this can be done without needing to, for example,perform any DNS queries in response to the Attach Request. In addition,to address changes in the DNS server, an MME 118 can use timers toperiodically refresh the locally stored information identifyingassociations between TAI and S-GWs.

Some embodiments combine reduced latency for S-GW selection and reducedlatency for TAI list allocation. For example, when an MME 118 receivesan Attach Request from a UE 110 via an eNB 112, the MME can use locallystored TAIs to S-GW mappings to select an S-GW serving the tracking areafrom which the UE is connected, and can use locally stored S-GW to TAImappings to determine a set of TAIs from which to allocate a trackingarea list for the UE, after receiving an attach request.

Reducing Tracking Area Updates

If the TAI list assigned to a UE was not, for example, generated usingappropriate characteristics regarding the UE's movements, the UE canfind itself frequently in tracking areas that are not in its assignedTAI list. This can lead to the UE sending a high number of TAUs andwasting radio resources and UE and network computing power. For example,a cellular phone may move from (referring to FIG. 2) TA-3 to TA-2. If,for example, TA-2 is not in the cellular phone's tracking area list, thephone can send a tracking area update to an eNB 112. This trackingupdate will identify the current tracking area (i.e., TA-2) and the lasttracking area visited (i.e., TA-3). To reduce TAUs, some embodimentsmanage a TAI list by identifying particular tracking areas to which a UEis likely to move.

Some embodiments use the identity of last TAI visited, which is includedin Attach Requests and TAUs, to predict which tracking area a UE willmove to. An MME 118 can maintain a per S-GW serving area graph. An S-GWserving area can be a group of tracking areas that are served by anS-GW. There can be, for example, multiple S-GWs serving an S-GW servingarea. The nodes of the graph represent TAIs within the S-GW servingarea. A Node(i) is connected to Node(j). When a tracking area update orattach request is received at an MME, the current TAI (j) and Lastvisited TAI (i) are monitored and an edge (i, j) is given a weight equalto the total number of such requests received. The total number of TAUsand Attach Requests received at each node is also stored. Then theweight of an edge (i,j) is equal to its number of request divided by thetotal number of request. For example, for a TAI-A: if there were tentotal request and five of them were (B,A) then the graph for TAI-A wouldinclude an edge between node TAI-A to TAI-B with a weight of 0.5 (i.e.,5/10).

A sample graph and corresponding weighed adjacency matrix are shown inFIGS. 4 and 5. As shown in the graph and adjacency matrix, for example,the edge between the node for TAI-A and TAI-B has a weight of 0.5indicating that half of the UEs that moved out of TAI-A, from the S-GWserving area for which FIG. 4 pertains, moved to TAI-B. Similarly,twenty percent moved to TAI-F and twenty percent moved to TAI-C. In theexample of FIG. 4, the probability of moving between two nodes in eitherdirection is the same. For example, changes from (1) TAI-A to TAI-B; and(2) TAI-B to TAI-A both have the same probability (i.e., 50%). Otherembodiments, for example, can include two oppositely directed edgesbetween each pair of nodes indicating different probabilities based onthe direction of movement.

A TAI list can be computed using the method illustrated in FIG. 6.Starting from the adjacency matrix of FIG. 5, the TAI with maximumpriority is selected (TAI-B). Then, the weights between all the nodes towhich TAI-B is connected are updated. Using W(A,D) as an example,W(A,B), which is 0.5, is multiplied by W(B,D), which is 0.2, to obtain0.1. Then, 0.1 is added to the current W(A,D), which as shown by node Anot being directly connected to node D (or by the adjacency matrix ofFIG. 5), is 0; 0+0.1 equals 0.1, hence: {W(A,D)+=0.1 (0.5×0.2), newweight=0.1}}. The updated weights for node A's remaining neighbors arecalculated as: {W(A,F)+=0.15 (0.5×0.3), new weight=0.35}} and{W(D,F)+=0.06 (0.2×0.3), new weight=0.06}. After removing node TAI-B andupdating the weights of the various nodes, the adjacency matrix of FIG.7 is produced.

As shown, the edge between TAI-A and TAI-F has the highest value amongthe edges from TAI-A. As such, TAI-F is added to the TAI list, and theupdate weights are calculated: {W(A,C)+=0.07 (0.35×0.2), newweight=0.37}; {W(A,D)+=0.02 (0.35×0.06), new weight=0.12}; {W(A,E)+=0.10(0.35×0.3), new weight=0.10}; {W(C,D)+=0.01 (0.2×0.06), newweight=0.51}; {W(C,E)+=0.06 (0.2×0.3), new weight=0.06}; and{W(D,E)+=0.01 (0.06×0.3), new weight=0.31}. After removing TAI-F andupdating the weights, the adjacency matrix of FIG. 8 is produced.

As shown, the edge between and TAI-A and TAI C has the highest valueamong the edges from TAI-A. As such, TAI-C is added to the TAI, and theupdate weights are calculated: {W(A,D)+=0.19 (0.37×0.51), newweight=0.31}; {W(A,E)+=0.02 (0.37×0.06), new weight=0.12}; and{W(D,E)+=0.03 (0.51×0.06), new weight=0.34}. After removing TAI-C andupdating the weights, the adjacency matrix of FIG. 8 is produced. TAI-Dand TAI-E can then be added to the TAI list based on their respectiveweights in relation to TAI-A.

In the above example, the total number of TAIs was less than sixteen tobegin with, so in some embodiments the entire method would have beenskipped. However, for ease of explanation, a graph of only six nodes wasused. In addition, various embodiments can use different values for themaximum number of nodes to be added to the TAI list, based on, forexample, whether the UE's characteristics (e.g., high paging, lowpaging, high mobility, low mobility, etc.).

Reducing Paging

An MME 118 provides paging to UEs 110. An MME 118 is specified to send apage to all eNBs in a tracking area where the target UE was lastregistered. This can lead to a page being sent to a number of eNBs andsubsequently being transmitted over the paging channel by a number ofeNBs to find the target UE. If a tracking area assigned to a UE iscovered by a multitude of eNBs, when the network needs to page the UE,all the eNBs will be paged. This paging can waste radio resources andnetwork computing capacity. To reduce such a waste of resources, someembodiments provide improved paging, through TAI list management, bylimiting paging to a reduced set of eNBs.

An MME 118 can assign tracking areas to Tracking Area Groups (TAGs).Each tracking area in a TAG can be supported by the same set of eNBs.Edge weighted directed graphs of TAGs can be created, with two edges inopposite directions between two nodes. The edge weight w of an edge fromTAG(i) to TAG(j) is the number of EnodeBs in TAG(j) but not in TAG(i).For example, if TAG(A) consisted of EnodeB-1, EnodeB-2, and EnodeB-3;and if TAG(B) consisted of EnodeB-3 and EnodeB-4, then the edge fromTAG(A) to TAG(B) would have a weight of one (because TAG(B) includesEnodeB-4, which is not included in TAG(A)). Using the same example, theedge from TAG(B) to TAG(A) would be two (because TAG(A) includesEnodeB-1 and EnodeB-2, which TAG(B) does not). Thus, if the set of eNBsin TAG(i) is a subset of those in TAG(j), the weight from TAG(j) toTAG(i) is set to 0. The minimum weight of any edge is 0.

An example table is illustrated in FIG. 10 including columns of trackingareas 1010, eNBs supporting those tracking areas 1020, and tracking areagroups 1030. For example, TAI-1 is supported by eNB-A, eNB-B, and eNB-C,and TAI-1 is in tracking area group TAG-A. FIG. 11 illustrates thedirected adjacency matrix for FIG. 10, where the directions of edges gofrom columns 1110 to rows 1120. For example, the edge from TAG-A toTAG-B has a weight of zero, and the edge from TAG-B to TAG-A has aweight of two.

A TAI list can be computed using the method illustrated in FIG. 12. Forexample, using the data of FIGS. 10 and 11, if an ATTACH request isreceived from a UE 110 in TAI-1, TAI-5 is first added to the UE's TAIlist, because TAI-5 and TAI-1 belong to the same TAG (1210 of FIG. 12).Then, the method can enter the while loop, at 1211. And, TAG-C can beselected, at 1212, because it has minimal weight (in this example TAG-Band TAG-C have the same weight, so the tracking area with a highernumber of TAIs can be selected between the two; in this case TAG-C hastwo and TAG-B has only one). TAI-3 and TAI-4 are thus added to the TAIlist, at 1213 because they the members of TAG-C. Then, TAG-B isselected, adding TAI-2 to the TAI list, then TAG-D is selected and TAI-6is added.

Device Categorization

As discussed, an MME 118 can assign a TAI list to a UE based on, amongother things, for example, the UE's tracking area update (“TAU”) loadand/or paging load. For example, the method described in FIG. 6 isrelated to reducing tracking area updates by reducing the number of TAIsincluded a UE's TAI list, and the method described in FIG. 12 is relatedto reducing paging load by, for example, reducing the number of eNBs 112that are paged when a network pages a UE. Also as discussed above, UE'scan be classified into various categories, including (1) low mobilitydevices; (2) high mobility, low paged devices; and (3) high mobility,high paged devices. Some embodiments can categorize a device into one ofthese categories, and based on its categorization, select a method orcombination of methods to use for generating the UE's TAI list.

At 1310 of FIG. 13, for example, an MME 118 can collect data useful forUE categorization. The collected data can include, for example, thenumber of times the UE's TAI has changed per unit of time 1311. Thisnumber can be determined based on the 51 messages exchanged between a UEand a network that include the current TAI of the UE. The collected datacan also include, for example, the number of times a UE is paged perunit of time. The collected data can be stored in MME as collected data1320.

Based on collected data 1320, a UE can be categorized, at 1330, into forexample, one of the three categories described above, and a TAI list canbe generated using method 1341, 1342, or 1343. Regarding, method 1343,for example, the methods described in FIGS. 6 and 12 can be combined invarious ways, such as, (1) using both and then selecting only TAIs thatappear each of the two generated TAI lists; (2) using the output of onemethod as input to another; (3) using both methods, weighing the resultsbased how mobile and/or how high paging the device is, to select some ofthe TAIs identified in the two generated lists; (4) various combinationsof (1)-(3), etc.

Other Example Embodiments

The various methods described herein, for example, identify S-GWs orgenerate TAI lists can be combined with various other methods. Forexample, the TAI lists generated by the methods described herein are notnecessarily the TAI lists allocated to user equipment. Instead, thegenerated TAI lists can be, for example, used as starting point forother methods to further process before being allocated to userequipment. Accordingly, a tracking area list for a user equipmentdevice, for example, can be, but is not limited to, a tracking area listallocated to a user equipment device, a tracking area list that is usedas input to additional methods, a tracking area list that is generatedto include a subset of TAIs generated by other methods, or a trackingarea list that is not allocated to a user equipment device.

Various embodiments of the disclosed subject matter can be implementedusing, and combined with, subject matter described in, for example, 3GPPTS 23.401, 3rd Generation Partnership Project; Technical SpecificationGroup Services and System Aspects; General Packet Radio Service (GPRS)enhancements for Evolved Universal Terrestrial Radio Access Network(E-UTRAN) access (Release 9), and related specification currentlyavailable from the 3rd Generation Partnership Project (3GPP). However,various embodiments can also be implemented using, and combined with,for example, systems, networks, devices, protocols, and standardsdifferent than described by these specifications.

Although the invention has been described and illustrated in theforegoing illustrative embodiments, it is understood that the presentdisclosure has been made only by way of example, and that numerouschanges in the details of implementation of the invention can be madewithout departing from the spirit and scope of the invention, which islimited only by the claims that follow. Features of the disclosedembodiments can be combined and rearranged in various ways within thescope and spirit of the invention.

What is claimed is:
 1. A method for selecting a serving gateway toservice user equipment in communication with a network, comprising:receiving a message from a base transceiver station including a list oftracking areas handled by the base transceiver station; initiating adomain name system query for at least one tracking area in the list oftracking areas to identify information indicating a serving gatewayserving the at least one tracking area; storing, in local memory, theinformation indicating the serving gateway serving the at least onetracking area; and upon an occurrence of a triggering event, retrieving,from the local memory, the stored information indicating the servinggateway serving the at least one tracking area.
 2. The method of claim1, wherein the message from the base transceiver station including thelist of tracking areas includes an S1 setup message.
 3. The method ofclaim 1, further comprising storing the information indicating theserving gateway serving the at least one tracking area includes storingthe information as at least part of a table of sets of tracking areaidentities and at least one associated serving gateway.
 4. The method ofclaim 3, wherein, for at least some tracking area identities, there isone and only one associated serving gateway.
 5. The method of claim 3,wherein at least some serving gateways are associated with more than onetracking area identifier.
 6. The method of claim 1, wherein thetriggering event includes a receipt of an attach request from the basetransceiver station identifying the user equipment and a tracking areafrom which the user equipment is connected to the network.
 7. The methodof claim 6, wherein the attach request includes an S1 initial userequipment message.
 8. The method of claim 1, wherein the basetransceiver station includes an evolved nodeB.
 9. The method of claim 1,further comprising periodically initiating the domain name system queryfor the at least one tracking area to periodically update the storedinformation indicating the serving gateway serving the at least onetracking area.
 10. The method of claim 1, wherein initiating the domainname system query for the at least one tracking area includes initiatingthe domain name system query using a tracking area identity fullyqualified domain name associated with the at least one tracking area.11. A mobility management entity in a communication network comprising:memory; an interface configured to receive a message from a basetransceiver station including a list of tracking areas handled by thebase transceiver station, to initiate a domain name system query for atleast one tracking area in the list of tracking areas to identifyinformation indicating a serving gateway serving the at least onetracking area; wherein the mobility management entity is configured tostore, in the memory, the information indicating the serving gatewayserving the at least one tracking area, and upon an occurrence of atriggering event, retrieving, from the memory, the stored informationindicating the serving gateway serving the at least one tracking area.12. The mobility management entity of claim 11, wherein the message fromthe base transceiver station including the list of tracking areasincludes an S1 setup message.
 13. The mobility management entity ofclaim 11, wherein the mobility management entity is configured to storethe information as at least part of a table of sets of tracking areaidentities and at least one associated serving gateway.
 14. The mobilitymanagement entity of claim 13, wherein, for at least some tracking areaidentities, there is one and only one associated serving gateway. 15.The mobility management entity of claim 13, wherein at least someserving gateways are associated with more than one tracking areaidentifier.
 16. The mobility management entity of claim 11, wherein thetriggering event includes a receipt of an attach request from the basetransceiver station identifying the user equipment and a tracking areafrom which the user equipment is connected to the network.
 17. Themobility management entity of claim 16, wherein the attach requestincludes an Si initial user equipment message.
 18. The mobilitymanagement entity of claim 11, wherein the base transceiver stationincludes an evolved nodeB.
 19. The mobility management entity of claim11, wherein the mobility management entity is configured to periodicallyinitiate the domain name system query for the at least one tracking areato periodically update the stored information indicating the servinggateway serving the at least one tracking area.
 20. The mobilitymanagement entity of claim 11, wherein the mobility management entity isconfigured to initiate the domain name system query using a trackingarea identity fully qualified domain name associated with the at leastone tracking area.